Gregor Samsa
The protagonist. A traveling salesman who transforms into an insect on the first page. He remains emotionally and mentally human throughout, caring about his family even as they abandon him. His passivity before and after the transformation is the book's central tragedy.
Grete Samsa
Gregor's younger sister. She starts as his primary caretaker and the family member most willing to engage with his new reality. By the end, she is the one who declares him no longer human. Her arc from compassion to rejection is the sharpest character change in the novella.
The Father
Gregor's father, who had seemed passive and defeated before the transformation. Once Gregor can't work, the father reasserts himself, gets a job, and becomes the household's physical authority. He is the most openly hostile to Gregor, twice using force against him.
The Mother
Gregor's mother wants to maintain her connection to her son but is physically unable to be in the same room as his insect form without fainting. She represents a kind of love that is real but too fragile to survive the situation.
The Charwoman
The cleaning woman hired after the family's regular servant leaves. She is the only character not frightened of Gregor. She interacts with him bluntly and without sentiment, and she is the one who finds his body and reports his death to the family.